package com.wj.community.util;

import org.apache.commons.lang3.CharUtils;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;

/**
 * @author: WangJin
 * @description 定义敏感词数据结构
 * @date: 2021/9/22 9:43
 */
@Component
public class SensitiveFilter {

    private static final Logger logger = LoggerFactory.getLogger(SensitiveFilter.class);

    //替换符
    private static final String REPLACEMENT = "***";

    //棍节点
    private TrieNode rootNode = new TrieNode();

    @PostConstruct //初始化方法
    public void init(){
        try (
            InputStream is = this.getClass().getClassLoader().getResourceAsStream("sensitive-words.txt");
            BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        ){
            String keyword;
            while((keyword = reader.readLine()) != null ){
                //添加到前缀树
                this.addkeyword(keyword);
            }
        } catch (Exception e) {
            logger.error("加载敏感词文件失败：" + e.getMessage());
        }
    }

    //将一个敏感词添加到前缀树中去
    private void addkeyword(String keyword){
        TrieNode tempNode = rootNode;
        for (int i = 0; i < keyword.length(); i++){
            char c = keyword.charAt(i);
            TrieNode subNode = tempNode.getSubNode(c);

            if(subNode == null){
                //初始化子节点
                subNode = new TrieNode();
                tempNode.addSubNode(c,subNode);
            }
            //指向子节点，进行下一轮循环
            tempNode = subNode;

            //设置结束标识
            if(i == keyword.length() - 1){
                tempNode.setKeywordEnd(true);
            }
        }
    }

    public String filter(String text){
        if(StringUtils.isBlank(text)){
            return null;
        }
        //指针1
        TrieNode tempNode = rootNode;
        //指针2
        int begin = 0;
        //指针3
        int position = 0;
        //结果
        StringBuffer sb = new StringBuffer();

        while(position < text.length()){
            char c = text.charAt(position);

            //跳过符号
            if (isSymbol(c)) {
                // 若指针1处于根节点,将此符号计入结果,让指针2向下走一步
                if (tempNode == rootNode) {
                    sb.append(c);
                    begin++;
                }
                // 无论符号在开头或中间,指针3都向下走一步
                position++;
                continue;
            }

            // 检查下级节点
            tempNode = tempNode.getSubNode(c);
            if (tempNode == null) {
                // 以begin开头的字符串不是敏感词
                sb.append(text.charAt(begin));
                // 进入下一个位置
                position = ++begin;
                // 重新指向根节点
                tempNode = rootNode;
            } else if (tempNode.isKeywordEnd()) {
                // 发现敏感词,将begin~position字符串替换掉
                sb.append(REPLACEMENT);
                // 进入下一个位置
                begin = ++position;
                // 重新指向根节点
                tempNode = rootNode;
            } else {
                // 检查下一个字符
                position++;
            }
        }

        // 将最后一批字符计入结果
        sb.append(text.substring(begin));

        return sb.toString();
    }

    // 判断是否为符号
    private boolean isSymbol(Character c) {
        // 0x2E80~0x9FFF 是东亚文字范围
        return !CharUtils.isAsciiAlphanumeric(c) && (c < 0x2E80 || c > 0x9FFF);
    }

    //前缀树
    private class TrieNode{

        //关键词结束标志
        private boolean isKeywordEnd = false;
        //子节点(key是下级字符，value是下级结点)
        private Map<Character,TrieNode> subNodes = new HashMap<>();

        public boolean isKeywordEnd() {
            return isKeywordEnd;
        }

        public void setKeywordEnd(boolean keywordEnd) {
            isKeywordEnd = keywordEnd;
        }

        // 添加子节点
        public void addSubNode(Character c, TrieNode node) {
            subNodes.put(c, node);
        }

        // 获取子节点
        public TrieNode getSubNode(Character c) {
            return subNodes.get(c);
        }
    }
}
